Virtual networking devices in Linux
Can someone explain in detail what are the differences of veth pairs and tap interfaces and how these devices connect to linux bridge or openvswitch.
I found this: "Veth is a special net devices which were created in pair, I consider it as a method to change the traffic's direction, that is, when the out direction traffic is sent to veth device from Linux protocol stack, it was sent to another its mirror veth device, so the mirror one treats it as a in direction traffic and put it back to Linux protocol stack for further usage.
Tap device is logical net device but have different with any other one: it allows user space program directly injecting traffic into Linux protocol stack, as well as it can retrieve traffic from the stack. It opens a tunnel to Linux protocol stack at level 2(or tun device at level 3) in user space, the stack will consider data from user space as in direction traffic"
but it didn't gave me the whole picture.
thanks in advance!
Answer
Linux tap interfaces created with ip tuntap cannot be used to attach network namespaces to linuxbridges or the openvswitch so we need to depend upon veth pair.
Virtual Ethernet interfaces come in pairs, and they are connected like a tube—whatever comes in one veth interface will come out the other peer veth interface. As a result, you can use veth interfaces to connect a network namespace to the outside world via the “default” or “global” namespace where physical interfaces exist.
A TAP device, such as vnet0 is how hypervisors such as KVM and Xen implement a virtual network interface card (typically called a VIF or vNIC). An Ethernet frame sent to a TAP device is received by the guest operating system.